1. Field of the Invention
The present invention relates to the field of analytical test elements and methods, such as are useful in manual and automated diagnostic systems, and, more particularly, to multilayer analytical elements useful in the qualitative and quantitative determination of body fluid constituents and medicaments present in such body fluids.
2. Brief Description of the Prior Art
Test devices in the form of test strips and similar solid state analytical elements have become commonplace in the analysis of various types of samples, particularly biological fluids. Test strips designed for detecting clinically significant substances in biological fluids, such as serum and urine, have been advantageous in the diagnosis of disease.
Test strips of various types have been known and used for many years in a wide variety of fields, from the most familiar pH test paper devices to in vitro diagnostic devices for the detection of various urine and blood components such as glucose, protein, occult blood and so forth (e.g., as described in U.S. Pat. Nos. 3,164,534; 3,485,587; and 3,012,976). Reagent compositions found in such test strips, often having limited sensitivity, interact with the constituent or constituents to be determined by direct chemical reaction and are applied to the detection of substances that are present in liquid samples at concentrations in the millimolar range or above.